"Welding" Unknown Pot Metal

I've got a part I'd like to repair if for no other reason than to be able to do it. The value is much lower than my time.

It?s a die cast mystery alu-zinc part. From what I have read the BlueDemon/AlumiWeld/MuggyWeld/DuraFix class of aluminum "brazing" rod is the way to go due to its low melting point. I've used Muggy Weld and Dura Fix rod to bond known "aluminum" in the past. Usually 6061 or 5052. It works, but you pretty much have to be able to lay down the entire repair at once and leave it to cool. I may not be able to that with this part, but that's not where I ran into a stop on this part.

The way most of these rods is used is to heat the metal until its hot enough to melt the rod. Push it around until it wets out where you need it and let it cool. On this project the base part started to melt before it got hot enough to start melting the rod. I wiped wth acetoe and brushed thoroughly first. Same way I would prep to mig weld aluminum. I told the person who asked me to repair it (my dad) and he said he expected that and not to worry about it. Still I'd like to find a way if at all possible. It bugs me. I read one website were a guy claims to be able to weld any kind of potmetal with TIG, but the only other references I found was the same guy spamming his services on various web forums.

I took it over to a buddy of mine who does a bit of TIG welding and he gave it a go. He tried low current with AC TIG and the max set at 75 amps and used the foot pedal to start lower. The first thing I noticed watching was the arc was red. We double checked on a piece of known aluminum and got the expected blue white arc. The other thing is the arc danced wildly. Back to the aluminum and a normal looking arc. The other thing was it just didn't seem to puddle at all. When he walked the pedal a little bit higher it just blew out metal.

We still don't know what it is, but we turned on all the fans and exited his shop after that to let the smoke clear... and there was smoke.

Its going in the dumpster I think.

Sounds very much like a zinc die cast part. The red arc is a tell tale. If you have a very fine OA torch and some zinc wire..it can..can..depending on your skill level..weld it. But frankly...you would be better off filling in the break/voids etc with epoxy..and sand casting a new part.

Interestingly you are the only one who commented on the red arc. Not even on the Miller Welds Forum. I specifically mentioned it because I thought it was a huge diagnostic datum.

I don't know how well I can weld with a torch, but I have 3 or 4 welding tips. Oddly enough I didn't learn my initial torch welding with a welding tip. The farm mechanic who taught me wouldn't let me use one. He said, "You always have a cutting tip. You may not always have a welding tip handy. Here is how you adjust a cutting tip to weld." Then we proceeded to blow holes in a muffler and then patch over them with a clothes hanger.

I've never seen it because I know not to risk breathing zinc fumes.

"Red arc" - that's the spectral colours of zinc. I think of it as more like "lilac" colour. The quantum energy steps in zink's atomic structure cause it to throw out this lilac light. ie. the specific energy of the photons emitted is sensed by our eyes as the colour lilac. You see if if you try to weld heavily dip-galv'ed steel. The fume will cause "zink sweats" - which I have never had - and body can get rid of zink over time - so for a transient small exposure - not the greatest cause to dwell on in the general scheme of things.

If there were a "zink lamp", it would have this lilac colour.

Gunner Asch on Sat, 02 Feb 2019 14:11:17 -0800 typed in rec.crafts.metalworking the following:

If memory serves, that's one reason to drink whole milk after work.

Hi Gunner

The "best" I met of welding on heavy hot-dip zink galv. which was infeasible to remove was welding in new deck-supporting truss structure on a seaside holiday-town pier.

Because it is

• a truss with slender members not blocking or setting up eddies in the air

• there is a constant onshore breeze this was the one-and-only occasion where you really could keep your head out of the zink-fume plume and it was OK.

Welding transversely across the truss members, you could look at the weld end-on and manipulate the rod to puddle-up a correct-shaped fillet despite the galv. kicking the arc around and the fume kicking the weld-pool around. And the arc was very lilac coloured indeed...!

Best wishes, Rich S

Supplied milk was used to mitigate toxic metals exposure in UK historically but in living memory of senior tradesmen here.

How did you rust-proof your welds?

Old timers used buttermilk, even heard a story of some welders refusing to weld galvanized with out their daily ration of buttermilk. Today it is very hard to find buttermilk that is not low fat. AFAIK the fat is what helps mitigate the fume fever not the milk. So 4% whole milk is the modern substitute.

A few years back had a nice little side job welding galvanized. Did it outdoors with a box fan suspended about two or three feet behind my head. No mask... Tried the whole milk a few times and skipped it others and could not tell a difference.

Galv.-spray. Zink-rich paint. Only thing you can really do (?) Rich S

What, you didn't build a vacuum chamber around each weld area and use vapor deposition? Shame. LOL.

After welding some rust holes on the bed fenders of my truck I brushed cold galvanizing paint on sandblasted inner areas around the repair, with disappointing results. Although it didn't flake off, rust pinpoints appeared after a few years and slowly spread. New England roads are salted to melt ice.

The wheel wells were much easier to work on with the bed inverted and raised on blocks.

In UK, where mildish winters but a lot of salting with temperatures around zero C, galv.-spray over grit-blasted lasts only a couple of years or so. Maybe three of four - nice. But it's quick to blast back and respray. Do it as the summer goes on (warm and dry), mindful your vehicle will look after you as we tip into the long cold darkness.

Actually zinc is routinely flame sprayed in open air. (Vapor deposition is too slow for anything but very thin coatings anyhow.)

First hit I found, a bit more searching should turn up details. The equipment is expensive, but entire bridges have been coated with this method in corrosive coastal areas where paint has a short lifetime.

Not really practical for the home or small shop unfortunately.

Glen

Sounds like drinking heavy whipping cream might be even better (googlegooglegoogle at least 36% fat).